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Title / Demonstrate knowledge of water treatment filtration processes
Level / 4 / Credits / 10
Purpose / People credited with this unit standard are able to demonstrate knowledge of: the purpose and principles of filtration; rapid sand filters; membrane filtration; and other filtration methods, in water treatment.
Classification / Water Industry > Water Treatment
Available grade / Achieved
Explanatory notes
Legislation and references relevant to this unit standard include:
Health and Safety at Work Act 2015, Hazardous Substances and New Organisms (HSNO) Act 1996, and subsequent amendments;
Drinking-water Standards for New Zealand, 2005 (Revised 2008). Ministry of Health, Wellington;
Guidelines for Drinking-water Quality Management for New Zealand 2015 (2nd ed). Ministry of Health, Wellington.
Outcomes and evidence requirements
Outcome 1
Demonstrate knowledge of the purpose and principles of filtration in water treatment.
Evidence requirements
1.1 The purpose of filtration in water treatment is described in terms of particulate removal.
1.2 Filtration methods are described in terms of the impact of filter loading.
Range rapid sand, membrane cartridge.
1.3 The removal mechanisms in filtration are described in terms of their processes.
Range includes but is not limited to – straining, adsorption, filter ripening, aperture size.
Outcome 2
Demonstrate knowledge of rapid sand filters in water treatment.
Evidence requirements
2.1 Rapid sand filters are outlined in terms of the design options used in New Zealand water treatment plants.
Range flow paths, filter floors, sand size, alternate media, uniformity coefficient, multi-media, media depth, head loss build-up, floc shear, backwash, pressure filler, automatic valveless gravity.
2.2 Rapid sand filter operating mode options are described in terms of flow and head loss versus filter run time.
Range filtration loading rate calculation, rising head, declining rate, flow balancing, filter ripening.
2.3 Rapid sand filter operating backwashing is described in terms of start points and sequence options.
Range start points – time, flow, turbidity, head loss;
sequence options – air scour, water wash, combined air water wash.
2.4 Operating problems of rapid sand filters are described in terms of their probable causes and remedies.
Range problems – mudballing, filter cracking, air blinding, floc carryover, turbidity, breakthrough spikes;
causes – poor backwashing, high poly doses;
remedies – improved backwashing, caustic/acid soaking.
Outcome 3
Demonstrate knowledge of membrane filtration in water treatment.
Evidence requirements
3.1 Membrane filtration is described in terms of membrane material options in New Zealand water treatment plants.
Range cartridge membranes, synthetic membranes, bag filters.
3.2 Filtration size terms are defined in terms of pore size and specification.
Range pore size – microfiltration, ultrafiltration, nanofiltration;
specification – nominal, absolute.
3.3 Membrane filtration plants are described in terms of design options and plant layout in New Zealand water treatment plants.
Range includes but is not limited to – filament bundles, flow path, crossflow, direct, submerged, vacuum pressure, capacity.
3.4 Membrane filter plant operations are described in terms of backwash initiation, cleaning factors, and integrity testing.
Range head loss increases, run times, air scour, filament failure checks, pressure decay test.
Outcome 4
Demonstrate knowledge of other filtration methods in water treatment.
Evidence requirements
4.1 Slow sand filtration is described in terms of its concept, components and effectiveness.
Range typical design, schmutzdecke layer, ripening, cleaning, final water quality.
4.2 Diatomaceous earth filtration is described in terms of its concept, components and effectiveness.
Range septums, pre-coat, cleaning, final water quality, pressure and vacuum systems.
4.3 Granular activated carbon (GAC) filtration is described in terms of its concept, components and effectiveness.
Range typical design, GAC media, adsorption, final water quality.
4.4 Ion exchange filtration is described in terms of its concept, components and effectiveness.
Range typical design, media, cartridge options, reactivation, zeolites, iron/manganese/hardness removal, final water quality.
Planned review date / 31 December 2021Status information and last date for assessment for superseded versions
Process / Version / Date / Last Date for Assessment /Registration / 1 / 1 February 2001 / 31 December 2018
Review / 2 / 19 September 2008 / 31 December 2018
Review / 3 / 16 March 2017 / N/A
Consent and Moderation Requirements (CMR) reference / 0101
This CMR can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Please note
Providers must be granted consent to assess against standards (accredited) by NZQA, before they can report credits from assessment against unit standards or deliver courses of study leading to that assessment.
Industry Training Organisations must be granted consent to assess against standards by NZQA before they can register credits from assessment against unit standards.
Providers and Industry Training Organisations, which have been granted consent and which are assessing against unit standards must engage with the moderation system that applies to those standards.
Requirements for consent to assess and an outline of the moderation system that applies to this standard are outlined in the Consent and Moderation Requirements (CMR). The CMR also includes useful information about special requirements for organisations wishing to develop education and training programmes, such as minimum qualifications for tutors and assessors, and special resource requirements.
Comments on this unit standard
Please contact the Infrastructure Industry Training Organisation if you wish to suggest changes to the content of this unit standard.
Infrastructure ITOSSB Code 101813 / Ó New Zealand Qualifications Authority 2017